JP2024035197A - Warp deformation prediction method, warp deformation prediction device, warp deformation prediction program, and recording medium for resin injection molded products - Google Patents

Abstract

[Problems] A method and apparatus for predicting warp deformation of resin injection molded products that can ensure sufficient prediction accuracy even for molded products with molding conditions and product specifications for which it is difficult to obtain sufficient prediction accuracy using conventional methods. A warp deformation prediction program and a recording medium are provided. [Solution] A method for predicting warp deformation of a resin injection molded product is a method of predicting warp deformation of a resin injection molded product using the finite element method through computer simulation. A model creation step S1 in which a model for flow analysis and a model for structural analysis are created by dividing into elements, and a flow analysis is performed using the model for flow analysis, the injection step S51, the pressure holding step S52, and the cooling step S51 are performed. A flow analysis step S2 of acquiring temperature information and pressure information of the resin in step S53, and a structural analysis step S3 of calculating the shrinkage behavior of the resin based on the temperature information and the pressure information using the structural analysis model. In the structural analysis step S3, the calculation start point of the shrinkage behavior calculation is set as the start point of the pressure holding step S52. [Selection diagram] Figure 4

Description

The present disclosure relates to a method for predicting warp deformation of a resin injection molded product, a warp deformation prediction device, a warp deformation prediction program, and a recording medium.

Conventionally, in order to improve the precision, efficiency, and cost reduction of product design in resin injection molded products, computer-aided engineering (CAE) has been used to analyze the flow and solidification behavior of the resin in the mold and the warping deformation of the final product. -Engineering) (for example, see Patent Documents 1 and 2).

Patent Document 1 discloses a method for predicting the shape of an injection molded product, which includes a first thermoviscoelastic analysis step and a second thermoviscoelastic analysis step. In the first thermoviscoelastic analysis step, the temperature and pressure at the start of resin contraction calculated based on the resin flow analysis, and the shrinkage strain of the resin calculated from the specific volume at every minute time after the start of resin contraction. is loaded, and by structural analysis of the mold and injection molded product, the amount of deformation, temperature, and stress of the injection molded product within the mold from the start of resin contraction to the opening of the mold are calculated at minute intervals. In the second thermoviscoelastic analysis process, the amount of deformation, temperature, and stress obtained in the first thermoviscoelastic analysis process are read, and the structural analysis of the injection molded product, which has no constraint conditions due to the mold, is performed. The deformation of the injection molded product is analyzed at minute intervals until the temperature reaches the outside temperature.

In the method for predicting the molding shrinkage rate of an injection molded product disclosed in Patent Document 2, the temperature when the pressure inside the molded product becomes atmospheric pressure is determined from data regarding shrinkage warpage analysis. Then, by multiplying the linear expansion coefficient by the difference between that temperature and the room temperature, the amount of linear contraction ΔL (P(t), T(t, th)) in a minute area within the product is estimated. As a result, the amount of shrinkage and warpage of the molded product is finally determined.

Japanese Patent Application Publication No. 2007-045118 Japanese Patent Application Publication No. 2007-083602

In conventional warp deformation analysis, the points at which the resin starts to shrink (Patent Document 1), the point at which the pressure inside the molded product reaches atmospheric pressure (Patent Document 2), and the point at which the resin temperature drops to a predetermined temperature such as the solidification temperature are analyzed. The amount of resin shrinkage is calculated based on temperature, pressure, specific volume, etc. The concept of the starting point of calculation for warp deformation analysis is based on the premise that the product is solid and that the calculation of the amount of shrinkage starts from the solidified part.

That is, the conventional method does not take into account the shrinkage behavior of the molten resin when the pressure of the resin exceeds atmospheric pressure. For this reason, the conventional method employs a calculation algorithm that performs coefficient correction to correct the difference between the actual molding and the predicted result at the final stage of analysis. Since the coefficients used in such a calculation algorithm depend on the molding conditions, there is a problem in that the difference in pre-actual warping deformation becomes excessive depending on the molding conditions. Further, since the product specifications to which the calculation algorithm can be applied are limited, such as small changes in plate thickness over the entire product, there is a problem in that prediction accuracy is significantly reduced depending on the product specifications.

Therefore, the present disclosure describes a method for predicting warp deformation of resin injection molded products that can ensure sufficient prediction accuracy even for molded products with molding conditions and product specifications for which it is difficult to obtain sufficient prediction accuracy with conventional methods, and a method for predicting warpage deformation. The present invention aims to provide a device, a warp deformation prediction program, and a recording medium.

In order to solve the above problems, a method for predicting warp deformation of a resin injection molded product according to an embodiment of the present disclosure is a method of predicting warp deformation of a resin injection molded product using a finite element method through computer simulation. A model creation process in which the shape data of the mold cavity is divided into multiple minute elements to create a flow analysis model and a structural analysis model, and a flow analysis is performed using the flow analysis model. , a flow analysis step of acquiring temperature information and pressure information of the resin in the injection step, pressure holding step, and cooling step; and a flow analysis step of acquiring temperature information and pressure information of the resin in the injection step, pressure holding step, and cooling step; and a structural analysis step of performing a behavior calculation, and in the structural analysis step, the calculation start point of the shrinkage behavior calculation is set as the start point of the pressure holding step.

According to this configuration, by setting the calculation start point of the shrinkage behavior calculation as the start point of the pressure holding process, it is possible to consider the influence of the molten resin on the amount of shrinkage when the pressure exceeds atmospheric pressure. . Further, the supplementary state of additional resin in the pressure holding process can also be taken into consideration. In this way, the prediction accuracy of warp deformation can be improved.

In the structural analysis step, it is preferable to determine that the resin is in a molten state when the temperature of the resin exceeds a predetermined temperature, and that the resin is in a solidified state when the temperature is below the predetermined temperature.

According to this configuration, since it is possible to determine whether the resin is in a molten state or a solidified state by a simple method, the calculation process can be simplified.

Furthermore, in an element in which the resin is in a molten state and the pressure of the resin exceeds atmospheric pressure, it is preferable to consider at least one of expansion and contraction of the resin.

According to this configuration, in a situation where the pressure applied to the resin exceeds atmospheric pressure, the shrinkage behavior of the resin in a molten state can be effectively taken into consideration. In this way, the prediction accuracy of warp deformation can be improved.

The pressure holding step includes a pressurized state in which the pressure is increased by supplementing with additional resin, and a holding state in which the pressure is maintained while the additional resin is supplemented, and the cooling The step includes a reduced pressure state in which the pressure decreases due to the stoppage of replenishment of the additional resin, and in the structural analysis step, the increase in pressure is determined based on the rate of change of the pressure per time Δp/Δt. Either the pressure state, the holding state, or the reduced pressure state may be determined, and at least one of expansion and contraction of the resin may be taken into consideration.

According to this configuration, the shrinkage behavior of the resin in the pressure holding process and the cooling process can be considered accurately.

In the structural analysis step, if it is determined that the resin is in a solidified state and the pressure of the resin exceeds atmospheric pressure, it is assumed that the resin does not shrink, and the pressure of the resin is In the case of atmospheric pressure, it is preferably assumed that the resin contracts.

In a situation where pressure exceeding atmospheric pressure is applied, it is thought that only the resin near the cavity surface of the mold is in a solidified state. In this case, it can be assumed that the solidified resin does not shrink because it is pressed against the cavity surface of the mold by the supplemented molten resin. This simplifies the calculation process.

It is preferably assumed that when the resin is in a molten state and the pressure of the resin is atmospheric pressure, the resin will contract.

According to this configuration, the prediction accuracy of warp deformation can be further improved.

Preferably, the shrinkage behavior calculation of the resin is performed using a linear expansion coefficient.

According to this configuration, the prediction accuracy of warp deformation can be further improved.

It is preferable to consider the amount of shrinkage due to a change in temperature in the holding state at the time when the pressure decreases to atmospheric pressure.

The resin shrinks in accordance with the PVT characteristics as the temperature decreases, from the temperature at which it is melted in a molding machine to room temperature. In the holding state in the pressure holding step, since pressure is applied as additional resin is supplemented, the amount of contraction due to the temperature change is apparently canceled by the amount of contraction due to the pressure change (the amount of compensated resin). However, since the pressure load applied in the held state is temporary, the prediction accuracy will be degraded if the analysis is performed without taking into account the amount of contraction due to the temperature change in the held state, or without taking it into account at all. Therefore, in this configuration, when the depressurization state of the cooling process ends and the pressure drops to atmospheric pressure, the amount of shrinkage corresponding to the temperature drop in the holding state is taken into consideration. Thereby, the prediction accuracy of warp deformation can be further improved.

The resin injection molded product is preferably a molded product in which a difference between a maximum value and a minimum value in at least one of the temperature distribution and the pressure distribution at a predetermined time after the start of the pressure holding step is a predetermined value or more. .

After the start of the pressure holding process, the difference between the maximum and minimum temperature values in the temperature distribution of the molded product is greater than or equal to a predetermined value, and/or the difference between the maximum and minimum pressure values in the pressure distribution of the molded product In a molded product in which the value is greater than a predetermined value, it is difficult for the entire molded product to shrink uniformly. Examples of molded products in which shrinkage progresses unevenly include molded products whose specifications such as plate thickness vary greatly depending on the part of the molded product, and those whose shapes are complex. Even in a molded product where the progress of shrinkage is uneven, according to this configuration, the amount of shrinkage in each part can be calculated with high accuracy, so the prediction accuracy of warp deformation can be effectively improved. .

In one embodiment, the resin injection molded product includes a sheet-like member disposed on the surface of the resin injection molded product and containing a component of a material different from the resin, and in the flow analysis step, the sheet-like member Thermal analysis of the members may be performed.

When the resin injection molded product includes a sheet-like member containing a component of a material different from the resin, the sheet-like member may have a shrinkage rate different from that of the resin. In this case, it is desirable to predict the warp deformation by taking into account the influence that the presence of the sheet-like member has on the shrinkage behavior of the resin injection molded product. In this configuration, by thermally analyzing the sheet-like member in the flow analysis step, it is possible to accurately predict warping deformation of a resin injection molded product having the sheet-like member on the surface.

Preferably, the sheet-like member is a continuous fiber sheet.

A continuous fiber sheet is a sheet formed by impregnating a plurality of fiber bundles with resin. By arranging a continuous fiber sheet on the surface of the injection molded product, the strength of the injection molded product can be improved. By using the resin material, it is possible to reduce the weight of the parts and increase the strength of the parts. In particular, by arranging continuous fiber sheets in the minimum necessary position, size, direction, etc., in areas where parts are easily damaged or where durability needs to be improved, high costs can be suppressed and effectively achieved. It is possible to improve the strength of parts. According to this configuration, it is possible to predict the effective attachment position, size, direction, etc. of the continuous fiber sheet in an injection molded product including the continuous fiber sheet.

Further, a warpage deformation prediction device for a resin injection molded product according to an embodiment of the present disclosure is a device that predicts warp deformation of a resin injection molded product using a finite element method through computer simulation, A model creation section that divides shape data into multiple minute elements to create a flow analysis model and a structural analysis model, and performs flow analysis using the flow analysis model to improve the injection process and pressure holding process. , a flow analysis unit that acquires temperature information and pressure information of the resin in the cooling process, and a structural analysis unit that calculates shrinkage behavior of the resin based on the temperature information and pressure information using the structural analysis model. The structural analysis unit is characterized in that the calculation start point of the shrinkage behavior calculation is the start point of the pressure holding step.

Furthermore, a program for predicting warp deformation of a resin injection molded product according to an embodiment of the present disclosure is a program for predicting warp deformation of a resin injection molded product using a finite element method through computer simulation, Step A of dividing the shape data of the mold cavity into a plurality of minute elements to create a flow analysis model and a structural analysis model, and performing a flow analysis using the flow analysis model, the injection process is completed. , calculating the shrinkage behavior of the resin based on the temperature information and the pressure information using the step B of acquiring temperature information and pressure information of the resin in the pressure holding step and the cooling step, and the structural analysis model. The method is characterized in that step C is executed, and in step C, the calculation start point of the shrinkage behavior calculation is set as the start point of the pressure holding step.

According to the above device and the above program, by setting the calculation start point of shrinkage behavior calculation as the start point of the pressure holding process, the influence of the molten resin on the shrinkage amount when the pressure exceeds atmospheric pressure. can also be considered. Further, the supplementary state of additional resin in the pressure holding process can also be taken into consideration. In this way, the prediction accuracy of warp deformation can be improved.

A recording medium according to an embodiment of the present disclosure is a computer-readable recording medium on which the above-described program for predicting warp deformation of a resin injection molded product is recorded.

As described above, according to the present disclosure, by setting the calculation start point of the shrinkage behavior calculation to the start point of the pressure holding process, it is possible to consider the influence of the resin in the molten state on the amount of shrinkage. Further, the supplementary state of additional resin in the pressure holding process can also be taken into consideration. In this way, the prediction accuracy of warp deformation can be improved.

A flowchart for explaining each step in resin injection molding. The graph which shows an example of the history of the pressure and temperature of resin in injection molding of resin. 1 is a diagram illustrating a configuration example of a warp deformation prediction device for a resin injection molded product according to Embodiment 1. FIG. 1 is a flowchart for explaining a method for predicting warp deformation of a resin injection molded product according to Embodiment 1. 5 is a table showing a calculation algorithm for calculating shrinkage behavior in the structural analysis process of FIG. 4. 6 is a diagram for explaining the concept of calculation in the pressurized state and depressurized state of FIG. 5. FIG. 6 is a diagram for explaining the concept of calculation in the pressurized state of FIG. 5. FIG. 6 is a diagram for explaining the concept of calculation in the holding state of FIG. 5. FIG. FIG. 3 is a perspective view of a test piece used for CAE analysis of the Example and Comparative Example of Experimental Example 1. 10 is a graph showing the history of resin pressure at representative portion X in FIG. 9; FIG. 9 is a cross-sectional view taken along line AA in FIG. 9; 10 is a graph showing the temperature history of resin in each layer of representative portion X in FIG. 9. FIG. 2 is a diagram illustrating (a) a molding process and (b) an example of the molded product of a film insert molded product having a continuous fiber sheet on the surface. FIG. 4 is a view corresponding to FIG. 4 when the injection molded product is a film insert molded product. (a) A plan view and (b) a cross-sectional view taken along the line AA, showing the shape of the sample used in Experimental Example 2. (a) A photograph of a cross section in the longitudinal direction at the center in the width direction of the sample of the reference example in Experimental Example 2, and (b) a graph plotting the lifting amount against the position in the longitudinal direction. 1 is a flowchart for explaining a conventional method for predicting warp deformation of a resin injection molded product. A table showing calculation algorithms for calculating shrinkage behavior in the conventional structural analysis process.

Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure, its applications, or its uses.

(Embodiment 1)
<Resin injection molding and resin injection molded products>
An overview will be given of resin injection molding and resin injection molded products that are targets of warp deformation prediction analysis according to the present embodiment. In addition, in this specification, the word "resin" means a resin composition containing a resin raw material and arbitrary additives.

-Resin injection molding-
FIG. 1 is a flowchart for explaining each step in resin injection molding. FIG. 2 is a graph showing an example of the history of resin pressure and temperature during resin injection molding.

As shown in FIGS. 1 and 2, resin injection molding includes an injection step S51, a pressure holding step S52, and a cooling step S53.

First, a molten resin material heated to a temperature _T1 is injected into a cavity formed by clamping a mold (not shown) (injection step S51).

When the entire cavity is filled with resin, supplementary injection of additional resin is started in order to reduce the amount of excessive shrinkage of the resin due to temperature drop (time A1). Then, a pressure exceeding atmospheric pressure P ₀ (herein, the amount of pressure exceeding atmospheric pressure P ₀ (P-P ₀ ) is also referred to as "pressure load") is applied to the resin in the cavity. . Then, while adjusting the amount of additional resin supplemented, the pressure of the resin is maintained at around a predetermined pressure _P1 (pressure holding step S52).

After a certain time or a certain amount of additional resin has been supplemented, the supplementation of additional resin is stopped (time A3). As a result, the pressure of the resin in the cavity gradually decreases from P ₁ and eventually reaches atmospheric pressure P ₀ (time A4). The molded product is cooled in the mold, removed from the mold by opening the mold, and then cooled in the atmosphere (cooling step S53).

Although not shown in FIG. 2, the molded product thus obtained is cooled to room temperature T ₀ and then subjected to post-processes such as deburring to become a product.

As shown in FIG. 2, the pressure holding step S52 includes a pressurized state B1 in which the pressure of the resin in the cavity is increased by supplementing with additional resin, and a holding state in which the pressure is maintained while the additional resin is supplemented. A state B2 is provided.

Furthermore, the cooling step S53 includes a reduced pressure state B3 in which the pressure decreases due to stopping the supplementation of additional resin.

In the pressure holding step S52 and the cooling step S53, the temperature of the resin becomes equal to or lower than the solidification temperature T ₂ (predetermined temperature) at an arbitrary time A2, although the time varies depending on the part or region of the molded product. That is, in a region or region where the temperature of the resin exceeds the solidification temperature _T2 , the resin is in a molten state, and in a region below the solidification temperature _T2 , the resin is in a solidified state. Note that the solidification temperature _T2 is not limited, and may be, for example, the crystallization temperature, glass transition temperature, melting point, etc. of the resin, or may be set by the user.

-Resin injection molded products-
The resin injection molded product is not particularly limited as long as it is a molded product manufactured by injection molding. Specific examples of resin injection molded products include parts for automobiles, rockets, aircraft parts, and sporting goods. Preferably, plate-shaped injection molded products such as interior and exterior members of vehicles are used.

The resin raw material is not particularly limited and may be any well-known resin, but specific examples include polypropylene resin, polycarbonate resin, polyester resin, polyamide (PA) resin, and the like. These resins may be used alone or in combination of two or more.

The resin may contain additives such as reinforcing fibers, fillers, pigments, dyes, impact modifiers, and UV absorbers. The reinforcing fibers are not particularly limited, and known fibers can be used, and specific examples include glass fibers, carbon fibers, cellulose nanofibers, and the like. These fibers may be used alone or in combination of two or more. The fiber diameter, fiber length, content, etc. of the reinforcing fibers, and the specifications, content, etc. of other additives are not particularly limited, and can be set to commonly used conditions. These additives may be added alone or in combination.

Note that the resin injection molded product may be an insert molded product, as described later in Embodiment 2.

Note that the method, device, and program for predicting warp deformation of a resin injection molded product according to the present embodiment predict the temperature distribution and pressure distribution of the resin at times after time A1 (see FIG. 2), which is the start point of the pressure holding step S52. It is preferable to apply the present invention to resin injection molded products in which the difference between the maximum value and the minimum value on at least one side is a predetermined value or more. Such resin injection molded products have limitations on molding conditions, large changes in thickness depending on the part of the product, and complex product shapes, so the resin injection molding process is difficult in the holding process S52 and/or the cooling process S53. It is a molded product with a wide range of temperature distribution and/or pressure distribution. In such a molded product, shrinkage tends not to proceed uniformly in the pressure holding step S52 and the cooling step S53. The present method can be preferably applied even to molded products in which the progress of shrinkage is uneven, and can obtain high prediction accuracy of warp deformation. Note that the predetermined value for the difference between the maximum value and the minimum value of the temperature distribution can be, for example, 5°C, preferably 10°C. The predetermined value of the difference between the maximum value and the minimum value of the pressure distribution can be, for example, 3 MPa, preferably 5 MPa.

<Warp deformation prediction device for resin injection molded products>
FIG. 3 shows a configuration example of a warp deformation prediction device 100 (hereinafter also referred to as “prediction device 100”) for a resin injection molded product according to the present embodiment. The prediction device 100 is a CAE (Computer Aided Engineering) system that has a computer 110 as its basic configuration. The prediction device 100 is a device that predicts warpage deformation of a resin injection molded product using a finite element method through computer simulation.

The prediction device 100 includes a storage unit 120 and a processor 130. The prediction device 100 also includes a display unit 140 such as a display, an input unit 150 such as a keyboard, and a reading unit 160 for acquiring information stored in various recording media 170. The storage unit 120 and/or the recording medium 170 store information such as programs for arithmetic processing and various data for analysis. The processor 130 performs various calculation processes based on the information stored in the storage unit 120, information input via the input unit 150, information acquired from the recording medium 170 via the reading unit 160, and the like.

The prediction device 100 uses the model creation unit 131 to create a flow analysis model and a structural analysis model by dividing shape data such as 3D CAD data defining a mold cavity into a plurality of minute elements. Note that the flow analysis model is a finite element model used for flow analysis, which will be described later. The structural analysis model is a finite element model used for structural analysis, which will be described later. The same model may be used as the flow analysis model and the structural analysis model, or different models may be used.

As the model creation section 131, commercially available automatic mesh creation software or the like can be used. Specifically, the model creation unit 131 includes, for example, 3D TIMON (registered trademark)-Pre/Post manufactured by Toray Engineering D Solutions Co., Ltd., FEMAP (registered trademark) manufactured by NST Corporation, and MSC Software. CAE preprocessors such as Patran (registered trademark) manufactured by Co., Ltd. and Hyeper mesh (registered trademark) manufactured by Altair Corporation can be used. Note that the shape and size of the element are not particularly limited, and are appropriately set according to the product specifications, material composition, calculation efficiency, and calculation accuracy level. Furthermore, a finite element model may also be created for the mold and subjected to analysis. When creating a finite element model of a mold, for example, a finite element model of only the surface forming the cavity of the mold or a part of the mold including the surface may be created.

Analysis conditions are set based on material property data regarding the type of resin, formulation, additives, various physical property values, etc., and boundary condition data that describes molding conditions such as injection speed and resin temperature during injection. Then, the flow analysis unit 133 performs flow analysis to analyze the behavior of the resin in the injection process S51, the pressure holding process S52, and the cooling process S53 using the above-described flow analysis model. Then, the flow analysis unit 133 acquires various data including temperature information, pressure information, etc. of the resin for each element and each minute time through the flow analysis. The acquired various data are stored in the storage unit 120. As the flow analysis section 133, injection molding CAE software such as 3D TIMON (registered trademark) manufactured by Toray Engineering D Solutions Co., Ltd. can be used, for example. Note that the minute time is an analysis unit time for flow analysis and structural analysis, and is not particularly limited, and is appropriately set according to the product specifications, material composition, calculation efficiency, and calculation accuracy level.

The structural analysis section 134 uses the above-described structural analysis model to calculate the shrinkage behavior of the resin based on the temperature information and pressure information of the resin calculated by the flow analysis section 133, and calculates the amount of shrinkage of the resin. As the structural analysis unit 134, solvers such as Abaqus manufactured by Dassault Systèmes, Inc. and 3D TIMON (registered trademark)-WARP manufactured by Toray Engineering D Solutions, Inc. can be used, for example.

<Method for predicting warpage deformation of resin injection molded products>
FIG. 4 is a flowchart showing the procedure for implementing the method for predicting warp deformation of a resin injection molded product (hereinafter also referred to as "the present prediction method") according to the present embodiment. This prediction method is a method of predicting warpage deformation of a resin injection molded product by computer simulation using the finite element method, and is performed using, for example, the above-mentioned prediction device 100.

As shown in FIG. 4, this prediction method includes, for example, a model creation step S1, a flow analysis step S2, and a structure analysis step S3.

First, in the model creation step S1, as described above, the model creation unit 131 creates a 3D
The mold cavity shape data created using CAD, etc. is divided into minute elements for numerical analysis, and a flow analysis model and a structural analysis model are created.

Next, in a flow analysis step S2, analysis conditions such as material property data and boundary condition data are set, and a flow analysis is performed using the above-described flow analysis model. Then, temperature information and pressure information are obtained for each resin element and for each minute time in each process in resin injection molding, that is, the injection process S51, the pressure holding process S52, and the cooling process S53.

Then, using the structural analysis model described above, the shrinkage behavior of the resin is calculated based on the temperature information and pressure information acquired in the flow analysis step S2, and the amount of shrinkage of the molded product in the pressure holding step S52 and the cooling step S53 is calculated. Calculate (structural analysis step S3).

The amount of shrinkage of the resin can be calculated based on the amount of change in volume due to change in temperature of the resin and the amount of change in volume due to change in pressure of resin. The shrinkage behavior calculation in the structural analysis step S3 is not particularly limited, but can be performed, for example, by the following process. That is, based on the temperature information and pressure information for each element of the resin and for each minute time obtained in the flow analysis step S2, the specific volume for each element and for each minute time is determined using an equation of state such as the Tait equation. Then, based on the temperature information, pressure information, and specific volume information for each element and each minute time, the linear expansion coefficient for each element and every minute time is calculated. The amount of shrinkage for each element and each minute time is calculated from the coefficient of linear expansion, and based on the amount of shrinkage, elastic modulus, stress, etc., the final warp deformation of the molded product is calculated using formulas such as generalized Hooke's law. Calculate the amount and shape of warp deformation. In addition, it is desirable to consider the anisotropy of contraction in the analysis.

Note that the structural analysis step S3 can include an in-mold shrinkage behavior calculation step S31 and an out-mold shrinkage behavior calculation step S32. The in-mold shrinkage behavior calculation step S31 is a step of calculating the shrinkage behavior of the molded product before demolding, and is performed in consideration of the influence of the mold. The out-of-mold shrinkage behavior calculation step S32 is a step of calculating the shrinkage behavior of the molded product after demolding, and is performed without considering the influence of the mold in the analysis.

Here, this prediction method is characterized by the calculation algorithm employed in the structural analysis step S3.

FIGS. 17 and 18 show an example of a conventional warp deformation prediction method. As shown in FIG. 17, the conventional warp deformation prediction method includes a model creation step S101, a flow analysis step S102, a structural analysis step S103, and a correction step S104. In the calculation algorithm adopted in the conventional structural analysis step S103, the calculation start point of the shrinkage behavior calculation is the point when the resin starts shrinking or the point when the pressure of the resin reaches atmospheric pressure. The point at which the resin apparently begins to shrink (the volume of the resin begins to decrease) is considered to be after the time at which the resin becomes solid, so the point at which the resin temperature T reaches the solidification temperature _T2 (in Figure 2) This can be considered as time A2). That is, in the conventional structural analysis step S103, as shown in FIG. 18, when the resin is in a solid state or the pressure P of the resin is atmospheric pressure P ₀ (P=P ₀ ), the resin contracts. Assuming that, the amount of contraction is calculated. On the other hand, when there is a pressure load in the pressure holding step S52 and the cooling step S53, that is, when the pressure P of the resin exceeds the atmospheric pressure P ₀ (P>P ₀ ), and when the resin is in a molten state, assumes that the amount of resin shrinkage is zero. After the structural analysis step S103, a correction step S104 is provided to correct the amount of shrinkage based on actual measurement data.

On the other hand, in the calculation algorithm adopted in the structural analysis step S3 of this prediction method, the calculation start point of the shrinkage behavior calculation is set to time A1, which is the start point of the pressure holding step S52.

Specifically, in the calculation algorithm of this prediction method, as shown in FIG. 5, when the resin pressure P is atmospheric pressure _P0 (after time A4 in FIG. 2), the resin is in a molten state. The amount of shrinkage is calculated assuming that the resin contracts both when it is in a solidified state and when it is in a solidified state.

In addition, in the calculation algorithm of this prediction method, the resin is in a molten state when the resin temperature T exceeds the solidification temperature T ₂ (predetermined temperature), and the resin is solidified when the temperature T is below the solidification temperature T ₂ (predetermined temperature). It is determined that the condition exists. According to this configuration, since it is possible to determine whether the resin is in a molten state or a solidified state by a simple method, the calculation process can be simplified. Note that the crystallization temperature of the resin is used as the solidification temperature _T2 .

If the pressure P of the resin exceeds the atmospheric pressure _P0 (after time A1 and before A4 in FIG. 2), that is, if there is a pressure load, the resin will contract when it is in a molten state. On the other hand, the amount of shrinkage is calculated on the assumption that the resin does not shrink when it is in a solid state.

First, the case where the pressure P of the resin exceeds the atmospheric pressure _P0 and the resin is in a molten state will be described.

When the pressure P of the resin exceeds the atmospheric pressure P ₀ and the resin is in a molten state, it is preferable to consider the shrinkage behavior of the resin in the molten state, that is, at least one of expansion and contraction of the resin.

Specifically, when there is a pressure load, as described above, the state is divided into a pressurized state B1, a holding state B2, and a reduced pressure state B3 (see FIG. 2).

In the calculation algorithm of this prediction method, these pressurized state B1, holding state B2, and depressurized state B3 are determined based on the rate of change of resin pressure P per time Δp/Δt. Specifically, as described above, as a result of the flow analysis, the pressure of the resin at every minute time is obtained as pressure information. Assuming that the pressure value at an arbitrary time t _n of the pressure information is P _n and the pressure value at the next time t _n+1 after time t _n is P _n+1 , Δt is the above-mentioned minute time, and Δt=t _n+1 − It is expressed as t _n . Then, Δp=P _n+1 −P _n , and the rate of change is expressed as Δp/Δt=(P _n+1 −P _n )/(t _n+1 −t _n ).

In the calculation algorithm of this prediction method, the pressurized state B1 is determined when Δp/Δt>a, the held state B2 is determined when |Δp/Δt|≦a, and the depressurized state B3 is determined when Δp/Δt<-a. . However, a is a real number greater than or equal to 0 (a≧0). a may be a fixed value or a value set by the user. Although the threshold value a of Δp/Δt [MPa/s] is not intended to be limited, it can be set to a value of, for example, 0.1 or more and 10 or less.

As shown in FIGS. 2 and 5, the temperature T of the resin gradually decreases in all of the pressurized state B1, the held state B2, and the reduced pressure state B3. Therefore, in any state, it is considered that the resin shrinks as the temperature T of the resin decreases.

On the other hand, the volume change (contraction or expansion) of the resin due to the application of a pressure load is considered to occur differently in the pressurized state B1, the held state B2, and the reduced pressure state B3.

Specifically, in the pressurized state B1, the pressure of the resin is increased due to the supplementation of additional resin. In this case, as shown in FIG. 6(a), considering the resin element 200 in a molten state, the resin of the element 200 is compressed by the pressure P (FIG. 6(b)), and the resin is added to the gap created by the compression. It can be assumed that the resin is replenished (FIG. 6(c)). That is, it is considered that a reaction force R corresponding to the compression due to the pressure P is generated in the element 200.

FIG. 7 is a diagram for explaining the reaction force R. For example, assume that the resin temperature is constant and that a space 303 (corresponding to a mold cavity) consisting of a container 301 and a piston 302 is filled with resin 401. At this time, it is assumed that the pressure load applied to the resin is P _x , the volume of the resin is V _x , and the mass of the resin is m _x . When the space 303 is filled with additional resin 402, the volume of the space 303 (corresponding to the volume of the cavity) does not change, that is, it can be considered that the piston 302 is fixed, so the resin 401 and the additional resin 402 The volume of remains unchanged at _Vx . On the other hand, as the additional resin 402 is supplemented, the pressure load applied to the resin 401 and the additional resin 402 increases from P _x to P _y (P _x < P _y ), and the mass of the resin filled in the space 303 increases. also increases from m _x to m _y (m _x < m _y ). In this state, if the pressure load is reduced (returned) from P _y to P _x , the volume of the resin 401 expands according to the PVT characteristics, and the volume of the additional resin 402 also expands. The volume of resin 401 and additional resin 402 then increases from V _x to V _z (V _x <V _z ).

In this way, specific volume is expressed as volume per unit mass, so in situations where additional resin is being supplemented, it is necessary to consider volume changes due to changes in resin mass in addition to volume changes due to changes in resin pressure. There is. That is, the above-mentioned reaction force R can be considered as a volume change due to a change in the mass of the resin, and can be considered using the compression due to pressure, that is, the compensated additional volumetric strain of the resin.

Therefore, when it is determined that the pressurized state is B1, the reaction force R is input into the analysis and reflected in the linear expansion coefficient. Specifically, regarding the above-mentioned reaction force R, the volumetric strain for compression is calculated from the PVT characteristics, and the volumetric strain is expanded by the volumetric strain.

Next, in the holding state B2, the change in pressure is suppressed to within a. In this case, as shown in FIG. 8, the supplemented additional resin is supplied to the center side in the plate thickness direction and flows (white arrow in FIG. 8). Due to the flow of the supplemented additional resin, a force is exerted that presses the resin on the mold M side against the surface of the mold M (solid line arrow in FIG. 8). Then, in the holding state B2, the amount of shrinkage due to the change in temperature is canceled by the compensated amount of resin, resulting in a situation where it appears that no shrinkage of the resin has occurred. However, since the pressure load applied in the holding state B2 is temporary, the prediction accuracy will decrease if the analysis is performed without considering the shrinkage amount due to the temperature change in the holding state B2 or without taking it into account at all. do.

Therefore, in the calculation algorithm of this prediction method, in the holding state B2, since additional resin is supplemented, it is assumed that there is no change in volume, and that the amount of contraction due to a change in pressure is zero. On the other hand, the amount of contraction corresponding to the temperature change in the holding state B2 is taken into consideration at the time when the pressure P decreases to the atmospheric pressure _P0 (time A4 in FIG. 2). Thereby, the prediction accuracy of warp deformation can be further improved.

In the reduced pressure state B3, since supplementation of additional resin is stopped, the amount compressed by the pressure load applied in the pressurized state B1 and the holding state B2 is released. Then, as the pressure decreases, the resin expands in accordance with the PVT characteristics (FIG. 6(d)).

To summarize the above, when the pressure P of the resin exceeds the atmospheric pressure _P0 and the resin is in a molten state, in the pressurized state B1, the resin contracts due to the temperature drop, and a reaction force occurs due to the compression due to the pressure P. Assuming that R occurs, it is reflected in the linear expansion coefficient.

In the reduced pressure state B3, the resin contracts due to the temperature drop, and the resin expands due to the pressure compression, which is reflected in the linear expansion coefficient.

Further, in the holding state B2, since additional resin is supplemented, the amount of compression due to pressure is calculated assuming that the amount of contraction is 0. Note that even in the holding state B2, resin shrinkage occurs due to the temperature drop, but the shrinkage amount for the temperature drop is only calculated from the PVT characteristics and stored in the storage unit 120, and at time A4, Reflected in linear expansion coefficient.

In other words, regarding the temperature decrease, a change in the volume of the resin is taken into consideration assuming that the resin contracts in all of the pressurized state B1, the holding state B2, and the reduced pressure state B3. On the other hand, regarding the pressure change, with a as the threshold value, the volume change of the resin is zero when |Δp/Δt|≦a (holding state B2), and |Δp/Δt|>a (pressurizing state B1 and depressurizing state Consider the volume change of the resin, assuming that the resin contracts or expands during B3).

Next, a case will be described in which the pressure P of the resin exceeds the atmospheric pressure _P0 and the resin is in a solid state.

In the pressurized state B1, the held state B2, and the depressurized state B3, it is thought that only the so-called skin layer, which is the resin near the surface forming the mold cavity, is in the solidified state (see FIG. 8). In this case, it is thought that the solidified resin is pressed against the cavity surface of the mold by the supplemented molten resin. Therefore, when the pressure P of the resin exceeds the atmospheric pressure _P0 and the resin is in a solid state, it can be assumed that the resin does not shrink (in terms of analysis, the amount of shrinkage=0). This configuration simplifies the calculation process.

As described above, according to the present prediction method, it is possible to consider the influence of the resin in the molten state on the amount of shrinkage in a situation where a pressure exceeding atmospheric pressure P ₀ is applied. Furthermore, the state of additional resin supplementation in the pressure holding step S52 can also be taken into consideration. In this way, it is possible to predict warp deformation with high accuracy without having to correct the amount of shrinkage based on actual measurement data, which is performed in the conventional warp deformation prediction method.

<Program for predicting warp deformation of resin injection molded products and its recording medium>
Each step of the warp deformation prediction method described above is programmed as a warp deformation prediction program. That is, the program for predicting warp deformation of a resin injection molded product according to the present embodiment allows the computer to perform the steps of each of the above steps, that is, step A of the model creation step S1, step B of the flow analysis step S2, and structural analysis step S3. This is a program that executes step C. This warp deformation prediction program can be executed by the control device 22 and the arithmetic device 26 while being stored in the storage device 25. Further, the warp deformation prediction program is not limited to being stored in the storage device 25, but can be recorded in various known computer-readable recording media, such as an optical disk medium or a magnetic tape medium. Then, by attaching such a recording medium to the reading device of the control device 22 and reading out the warp deformation prediction program, the program can be executed.

<Experiment example 1>
Next, regarding the aspect of Embodiment 1, a concrete example of an experiment will be described.

FIG. 9 shows the test piece TP (plate thickness 2 mm) used in the CAE analysis of Examples and Comparative Examples. The 3D CAD data of the shape of the test piece TP was divided into 3D solid elements to create a flow analysis model.

Next, a flow analysis was performed under the analysis conditions shown in Table 1, and pressure information and temperature information of the resin were obtained for each element and each minute time. 3D TIMON (registered trademark) manufactured by Toray Engineering D Solutions Co., Ltd. was used for the flow analysis. In FIG. 9, the position indicated by the symbol Y is the nozzle touch position. The cooling time in Table 1 is the time required from the start of the pressure holding process to the end of the reduced pressure state B3. After the end of reduced pressure state B3, that is, after the pressure of the resin reaches atmospheric pressure P ₀ , as a cooling process after demolding, heat radiation calculation is performed at an atmospheric temperature of 23°C for 2 hours from the end of reduced pressure state B3. I did it.

FIG. 10 shows the history of the resin pressure in the representative part X of the test piece TP in FIG. 9 from the start of the pressure holding process to the time when about 13 seconds have elapsed, which was obtained by the flow analysis. Note that the vertical axis in FIG. 10 indicates pressure load, and pressure load 0 corresponds to atmospheric pressure P ₀ . As shown in FIG. 10, the pressurized state B1 is from the start of the pressure holding process until approximately 0.4 seconds, the holding state B2 is from the end of the pressurizing state B1 to 5 seconds, and the depressurizing state is from the end of the holding state B2 to 8 seconds. It is B3.

FIG. 11 is a cross-sectional view taken along the line AA in FIG. 9, and schematically shows the layers L1 to L9 in the thickness direction of the representative portion X. Layer L1 is a layer that contacts the cavity surface that is the surface of the cavity mold, layer L9 is a layer that contacts the core surface that is the surface of the core mold, and layers L2 to L4 are the second, third, and fourth layers, respectively. Layer L5 is the central layer in the thickness direction, and layers L6 to L8 are the sixth, seventh, and eighth layers, respectively.

FIG. 12 shows the history of the resin temperature in each layer L1 to L9 after the start of the pressure holding process. As shown in FIG. 12, in the layers L1 and L9 that contact the cavity surface and the core surface, the temperature is 100°C or less from the start of the pressure holding process, and the solidification temperature of the polypropylene resin is set at _T2. It can be seen that the crystallization temperature is lower than 141°C. That is, in the layer L1 and the layer L9, the resin is considered to be in a solidified state from the start of the pressure holding process. Further, in the layer L2, layer L3, layer L7, and layer L8, the resin temperature becomes lower than the solidification temperature _T2 during the holding state B2, so it is considered that the resin changes from the molten state to the solidified state in the holding state B2. On the other hand, in layers L4 to L6 on the center side in the thickness direction, the resin is considered to change from a molten state to a solidified state in the reduced pressure state B3.

Note that FIGS. 10 and 12 show an example of the pressure history and temperature history, respectively, in the representative portion X, and the flow analysis provides a different pressure history and temperature history for each element of the flow analysis model. These are acquired as pressure information and temperature information and stored in the storage unit.

Next, for the test piece TP in FIG. 9, a structural analysis model was created using 3D solid elements (first-order hexahedral elements and first-order triangular prism elements). The pressure information and temperature information obtained in the above-mentioned flow analysis are assigned to each element of the structural analysis model, the structural analysis is performed, and the shrinkage rate and the inclination angle shown as θ ₁ and θ ₂ in FIG. 9 (hereinafter referred to as , the shrinkage rate and inclination angle are sometimes collectively referred to as "shrinkage rate, etc.") were calculated. In addition, the shrinkage rate is the volume (or When considering anisotropy, it is the ratio of the length in the corresponding direction.

For the structural analysis of the comparative example, 3D TIMON (registered trademark) manufactured by Toray Engineering D Solutions Co., Ltd. was used. Further, for the structural analysis of the example, an improved version of the analysis solver was used, which is based on Abaqus manufactured by Dassault Systèmes, and incorporates the calculation algorithm of the above-mentioned prediction method using a user subroutine. Note that the threshold value a of Δp/Δt [MPa/s] was set to 1. When the test piece TP is in the mold, in order to take into account the influence of the mold, a finite element model is created with only the surface shape of the mold as a constraint, and the friction coefficient is set to 0.5, and the mold surface and The structure is configured to perform contact determination. In addition, when the test piece TP was demolded and came out of the mold, arbitrary points were restrained to set analysis conditions that were not affected by the mold.

Further, as a reference example, a test piece TP having the same shape and the same material as the test piece TP used for the CAE analysis was actually manufactured by injection molding under the same conditions as the CAE analysis. Then, regarding the test piece TP of the reference example, the shrinkage rate etc. of each part were calculated and used as actual measured values.

The predicted and actual difference was calculated based on the shrinkage rate obtained by CAE analysis and the measured shrinkage rate. Specifically, the difference between the shrinkage percentage, etc. obtained by CAE analysis of the examples and comparative examples and the shrinkage percentage, etc. of the measured value is divided by the shrinkage percentage, etc. of the measured value, and the value is expressed as a percentage. Calculated as the difference between forecast and actual results. The results are shown in Table 2. Note that "MD1", "TD1", and "ND1" shown in Table 2 refer to the flow direction of the resin in the first portion TP1 of the test piece TP, the direction perpendicular to the flow direction, and the plate, respectively, as shown in FIG. Indicates thickness direction. In addition, "MD2", "TD2", and "ND2" shown in Table 2 refer to the flow direction of the resin in the second portion TP2 of the test piece TP, the direction perpendicular to the flow direction, and the plate, respectively, as shown in FIG. Indicates thickness direction.

As shown in Table 2, the shrinkage rate difference in both the first part TP1 and the second part TP2 is extremely small, especially in the plate thickness direction (ND1 and ND2), and the prediction accuracy is improved. understood. Furthermore, with regard to the inclination angles (θ ₁ and θ ₂ ), it was confirmed that the difference between the actual and expected values was reduced and the prediction accuracy was improved.

(Embodiment 2)
Other embodiments according to the present disclosure will be described in detail below. In the following description, the same parts as in the first embodiment are given the same reference numerals and detailed description will be omitted.

A resin injection molded product is an insert molded product that is formed by integrally molding an insert member that is placed in advance in a cavity and a base resin made of the above-mentioned resin raw material into the cavity where the insert member is placed. It's okay.

The insert member is not particularly limited, and may be a generally known member such as a metal member or a different type of resin member.

The insert member may be a sheet-like member that is placed on the surface of the resin injection molded product and includes a component of a material different from the base resin. That is, the insert molded product may be a film insert molded product.

Examples of sheet-like members include continuous fiber sheets. A continuous fiber sheet is a sheet formed by impregnating a plurality of fiber bundles with resin. By arranging a continuous fiber sheet on the surface of the injection molded product, the strength of the injection molded product can be improved. By using the resin material, it is possible to reduce the weight of the parts and increase the strength of the parts. In particular, by arranging continuous fiber sheets in the minimum necessary position, size, direction, etc., in areas where parts are easily damaged or where durability needs to be improved, high costs can be suppressed and effectively achieved. It is possible to improve the strength of parts.

The fiber bundle in the continuous fiber sheet is not particularly limited, and at least one type of fiber bundle consisting of glass fiber, carbon fiber, cellulose fiber, aramid fiber, etc. can be employed. The direction of the fiber bundle is not particularly limited. That is, the continuous fiber sheet may be a generally known sheet such as a unidirectional (UD) type or a woven type.

The impregnated resin in the continuous fiber sheet can be the same resin as the resin material described above. The impregnating resin is preferably the same type of resin as the base resin, although this is not intended to be limiting. Specifically, for example, when the base resin is polypropylene resin, nylon resin, etc., it is preferable that the impregnating resin of the continuous fibers is also polypropylene resin, nylon resin, etc., respectively.

FIG. 13 shows an example of an insert molding process and an insert molded product when a continuous fiber sheet is attached to the surface of a resin injection molded product. As shown in FIG. 13(a), for example, a pre-formed continuous fiber sheet 501 is placed on the surface of a movable mold 602 in a cavity 604. With the mold clamped, molten base resin is injected into the cavity 604 through a gate 605 provided on the fixed mold 603, for example. As shown in FIG. 13(b), the obtained insert molded product 500 is a composite member including a base resin 502 and a continuous fiber sheet 501 disposed on the surface of the base resin 502. For example, when the continuous fiber sheet is a UD type and the fiber direction is the direction shown by the white double arrow in FIG. 13(b) (also referred to as the "fiber direction"), the physical properties of the continuous fiber sheet 501 are It has high rigidity, high tensile strength, and low linear expansion. On the other hand, in the direction perpendicular to the fiber direction (also referred to as "orthogonal direction"), the physical properties of the continuous fiber sheet 501 depend on the physical properties of the impregnated resin. Then, in the insert molded product 500, during cooling, the shrinkage rate in the fiber direction becomes smaller on the side of the base resin 502 closer to the continuous fiber sheet 501, and the shrinkage rate decreases as the distance from the continuous fiber sheet 501 increases and in the orthogonal direction. (See the solid line arrow in FIG. 13(b)). As a result, in the insert-molded product 500, the surface where the continuous fiber sheet 501 is present tends to warp in a convex shape (see FIG. 16(a)). Therefore, in such a film insert molded product, it is desirable to predict warpage deformation in consideration of the influence that the presence of the continuous fiber sheet has on the shrinkage behavior of the entire molded product.

FIG. 14 is a view corresponding to FIG. 4 when the injection molded product is a film insert molded product. The warpage deformation prediction method in this embodiment, like the first embodiment, includes, for example, a model creation step S1, a flow analysis step S2, and a structure analysis step S3. Furthermore, in addition to these steps, a comparison step S4, a determination step S5, and a determination step S6 may be provided.

In the model creation step S1, a flow analysis model and a structural analysis model of the desired design shape A are created according to the above-described procedure. In these models, the application position of the continuous fiber sheet, shrinkage rate, molding conditions, etc. are set as control factors.

Specifically, for example, setting of the pasting position of the continuous fiber sheet is performed by setting the element at the pasting position of the continuous fiber sheet on the solver to be used, that is, the model creation unit 131 and/or the flow analysis unit 133, if the element is the continuous fiber sheet. This can be done by defining that it is a sheet.

Next, in a flow analysis step S2, a flow analysis of the base resin in a molten state and a thermal analysis of the continuous fiber sheet are simultaneously performed. Specifically, for example, resin material data such as viscosity characteristics of the base resin, material data such as heat transfer coefficient and thermal conductivity of the continuous fiber sheet as a composite material, etc. are set, and the flow analysis unit 133 performs flow analysis and Perform thermal analysis. In this way, temperature information and pressure information for each element of the flow analysis model is obtained.

In the structural analysis step S3, the structural analysis section 134 performs structural analysis using the temperature information and pressure information according to the procedure described in the first embodiment. Then, the amount of shrinkage of the molded product is calculated. Then, a warped deformed shape B is obtained from the designed shape A by taking into account the calculated amount of shrinkage.

Next, a case including a comparison step S4, a determination step S5, and a determination step S6 will be described.

The warped deformed shape B obtained in the structural analysis step S3 is compared with the designed shape A (comparison step S4).

Then, it is determined whether the difference between the warped deformed shape B and the designed shape A satisfies the criteria (determination step S5).

If this difference in AB does not meet the criteria, for example, the process returns to the model creation step S1 and adjustments are made to control factors such as changing the continuous fiber sheet pasting position. Then, each process from the flow analysis process S2 to the determination process S5 is repeated until the difference between AB meets the standard.

On the other hand, if the difference between AB meets the criteria, it means that it has been confirmed that the design shape A set in the model creation step S1 is an allowable shape, so the design shape A and other conditions can be used as control factors. It is determined and the warpage deformation prediction is ended (determination step S6). By reflecting the control factors determined in this way on the mold shape, the design work of a desired part is completed, in which the amount of deformation is suppressed and the strength is improved due to the presence of the continuous fiber sheet.

The AB difference and its standard are not particularly limited, and can be set as appropriate in consideration of the type, size, performance, etc. of the component to be predicted. Specifically, the difference is, for example, the maximum value of the amount of deformation when comparing both A and B, the maximum value of the amount of deformation of a specific part such as the continuous fiber sheet pasting location, the average value of the amount of overall deformation, etc. can be mentioned. Specific examples of the criteria for the difference include upper limits of these maximum values, average values, and the like.

According to the warp deformation prediction method of the present embodiment, a continuous fiber sheet is provided on the surface by performing structural analysis using temperature information and pressure information obtained by performing thermal analysis of the continuous fiber sheet in the flow analysis step. Warpage and deformation of resin injection molded products can be predicted with high accuracy. Furthermore, it is possible to predict the effective attachment position, size, direction, etc. of a continuous fiber sheet in an injection molded product equipped with a continuous fiber sheet.

As in the first embodiment, each step in FIG. 14 can also be programmed as a warp deformation prediction program. Specifically, for example, the program for predicting warp deformation of a resin injection molded product according to the present embodiment causes a computer to perform the steps of each step in FIG. 14, that is, step A of the model creation step S1 and step B of the flow analysis step S2. , is a program for executing procedure C of the structural analysis step S3, procedure of the comparison step S4, procedure of the determination step S5, and procedure of the determination step S6.

<Experiment example 2>
Next, regarding the aspect of Embodiment 2, a concrete example of an experiment will be described. Note that matters and procedures not described below were the same as those in Experimental Example 1 above.

FIG. 15 shows the shape of a sample of an insert molded product 500 manufactured in a reference example and used in the CAE analysis of the examples and comparative examples. Further, Table 3 shows details of the materials, analysis conditions (molding conditions), etc. Note that the heat transfer coefficient of the continuous fiber sheet is a value set as the heat transfer coefficient between the continuous fiber sheet and the mold. Furthermore, the thermal conductivity of the continuous fiber sheet was input as the value of the composite material.

As shown in FIGS. 15(a) and 15(b), the shape of the sample was a flat plate with a width of 120 mm, a length of 375 mm, and a thickness of 2 mm. The gate 405 is located at the center in the width direction on one end side in the length direction of the sample. A continuous fiber sheet 501 with a width of 100 mm, a length of 215 mm, and a thickness of 0.15 mm is arranged on one side of the sample. The continuous fiber sheet 501 is attached at a position 30 mm from the gate 605 side in the length direction of the sample and 10 mm from both sides in the width direction of the sample. The base resin is polypropylene (PP) resin. The continuous fiber sheet 501 is a UD type PP-impregnated carbon fiber sheet, and the fiber direction is indicated by the white double arrow in FIG. 15(a).

The 3D CAD data of the shape of the sample was divided into 3D solid elements to create a flow analysis model. The element at the continuous fiber sheet attachment position in the flow analysis model was defined as the continuous fiber sheet.

Next, flow analysis and thermal analysis were performed under the analysis conditions shown in Table 3, and pressure information and temperature information of the resin and continuous fiber sheet were obtained for each element and each minute time. 3D TIMON (registered trademark) manufactured by Toray Engineering D Solutions Co., Ltd. was used for the flow analysis and thermal analysis. The cooling time in Table 3 is the time required from the start of the pressure holding process to the end of the reduced pressure state B3. After the end of reduced pressure state B3, that is, after the pressure of the resin reaches atmospheric pressure P ₀ , as a cooling process after demolding, heat radiation calculation is performed at an atmospheric temperature of 23°C for 2 hours from the end of reduced pressure state B3. I did it.

Structural analysis was performed using the pressure information and temperature information obtained as described above as input information. In addition, creation of the structural analysis model and structural analysis of the example and the comparative example were performed in the same manner as the example and the comparative example of Experimental Example 1, respectively.

FIG. 16(a) shows a photograph of a cross section in the longitudinal direction of the sample of the reference example at the center in the width direction indicated by the dashed line 500A in FIG. As shown in FIG. 16(a), the amount of deformation from the flat plate state at the upper end of the cross section 500A, that is, the end on the side where the continuous fiber sheet 501 exists, is defined as the lifting amount [mm], and the reference example, the example, and the It was measured or calculated for each of the comparative examples. FIG. 16(b) shows a graph in which this lifting amount is plotted against the position [mm] in the length direction with one end on the side of the gate 605 in the length direction being zero. Further, Table 4 shows the maximum value of the lifting amount (also referred to as "maximum lifting amount") and the position in the length direction giving the maximum lifting amount.

As shown in Figure 16(b) and Table 4, in the CAE analysis of the comparative example, the maximum uplift amount was extremely small compared to the actual measured value of the reference example, and the position in the length direction that gave the maximum uplift amount could not be reproduced. do not have. In particular, in FIG. 16(b), the amount of lifting is slightly negative at the position where the continuous fiber sheet is present, and it can be seen that the predicted warping is in the opposite direction to that of the reference example. In other words, it can be said that the CAE analysis of the comparative example was unable to reproduce the influence of the presence of the continuous fiber sheet on warp deformation almost at all.

On the other hand, in the CAE analysis of the example, although the maximum lifting amount was calculated to be slightly larger than the actual value of the reference example, it was possible to reproduce the occurrence of warping deformation in which the surface where the continuous fiber sheet is present becomes convex. . Furthermore, the position in the length direction that gives the maximum value of the maximum lifting amount can also be roughly reproduced. That is, it can be seen that in the CAE analysis of the example, it is possible to reproduce the influence that the presence of the continuous fiber sheet has on warp deformation.

In this way, in the flow analysis step S2, by using the temperature information and pressure information obtained by simultaneously performing the flow analysis of the base resin in the molten state and the thermal analysis of the continuous fiber sheet, it is possible to prepare a continuous fiber sheet on the surface. It was also shown that warping deformation of molded insert molded products can be predicted with high accuracy.

(Other embodiments)
In the first and second embodiments described above, the temperature dependence of Young's modulus may be taken into consideration in the shrinkage behavior calculation in the structural analysis step S3. Further, viscoelastic properties may be applied to the resin in a solidified state. Furthermore, the shape data of the mold may be modeled, and contact determination between the molded product and the surface forming the cavity of the mold may be added.

The present disclosure discloses a warpage prediction method and a warp deformation prediction device for resin injection molded products that can ensure sufficient prediction accuracy even for molded products with molding conditions and product specifications for which it is difficult to obtain sufficient prediction accuracy with conventional methods. , a warp deformation prediction program, and a recording medium, which is extremely useful.

100 Warp deformation prediction device for resin injection molded products 131 Model creation section 133 Flow analysis section 134 Structural analysis section 170 Recording medium 500 Insert molded product 501 Continuous fiber sheet (sheet-like member)
502 Base resin A1 Start time of pressure holding process B1 Pressurized state B2 Holding state B3 Depressurized state S1 Model creation process S2 Flow analysis process S3 Structural analysis process S4 Comparison process S5 Judgment process S6 Determination process S51 Injection process S52 Pressure holding process S53 Cooling process _T2 solidification temperature (predetermined temperature)
P ₀ atmospheric pressure

Claims (14)

A method for predicting warpage of a resin injection molded product using a finite element method through computer simulation, the method comprising:
a model creation process in which shape data of the mold cavity is divided into multiple minute elements to create a flow analysis model and a structural analysis model;
a flow analysis step of obtaining temperature information and pressure information of the resin in the injection process, pressure holding process, and cooling process by performing a flow analysis using the flow analysis model;
a structural analysis step of calculating shrinkage behavior of the resin based on the temperature information and the pressure information using the structural analysis model;
A method for predicting warpage deformation of a resin injection molded product, characterized in that, in the structural analysis step, the calculation start point of the shrinkage behavior calculation is set as the start point of the pressure holding step. In claim 1,
In the structural analysis step, it is determined that the resin is in a molten state when the temperature of the resin exceeds a predetermined temperature, and that the resin is in a solidified state when the temperature is below the predetermined temperature. A method for predicting warpage deformation of resin injection molded products. In claim 2,
A method for predicting warp deformation of a resin injection molded product, characterized in that in an element where the resin is in a molten state and the pressure of the resin exceeds atmospheric pressure, at least one of expansion and contraction of the resin is taken into account. In claim 3,
The pressure holding step includes a pressurized state in which the pressure is increased by supplementing with additional resin, and a holding state in which the pressure is maintained while the additional resin is supplemented,
The cooling step includes a reduced pressure state in which the pressure decreases due to the supplementation of the additional resin being stopped,
In the structural analysis step, one of the pressurized state, the holding state, and the depressurized state is determined based on the rate of change of the pressure per time Δp/Δt, and at least one of expansion and contraction of the resin is determined. A method for predicting warpage deformation of resin injection molded products. In claim 2 or claim 3,
In the case where it is determined that the resin is in a solidified state in the structural analysis step,
Assuming that the resin does not shrink when the pressure of the resin exceeds atmospheric pressure,
A method for predicting warp deformation of a resin injection molded product, characterized in that when the pressure of the resin is atmospheric pressure, it is assumed that the resin contracts. In claim 2 or claim 3,
A method for predicting warp deformation of a resin injection molded product, characterized in that the resin is assumed to contract when the resin is in a molten state and the pressure of the resin is atmospheric pressure. In claim 1 or claim 2,
A method for predicting warp deformation of a resin injection molded product, characterized in that the shrinkage behavior calculation of the resin is performed using a linear expansion coefficient. In claim 4,
A method for predicting warpage deformation of a resin injection molded product, characterized in that an amount of shrinkage due to a change in temperature in the holding state is taken into account at the time when the pressure decreases to atmospheric pressure. In claim 1 or claim 2,
The resin injection molded product is characterized in that the difference between the maximum value and the minimum value in at least one of the temperature distribution and the pressure distribution at a predetermined time after the start of the pressure holding process is a predetermined value or more. A method for predicting warpage deformation of resin injection molded products. In claim 1 or claim 2,
The resin injection molded product includes a sheet-like member disposed on the surface of the resin injection molded product and containing a component of a material different from the resin,
A method for predicting warpage deformation of a resin injection molded product, comprising performing a thermal analysis of the sheet-like member in the flow analysis step. In claim 10,
A method for predicting warp deformation of a resin injection molded product, wherein the sheet-like member is a continuous fiber sheet. A device for predicting warpage deformation of a resin injection molded product using a finite element method through computer simulation,
a model creation section that divides the shape data of the mold cavity into a plurality of minute elements to create a flow analysis model and a structural analysis model;
a flow analysis unit that obtains temperature information and pressure information of the resin in an injection process, a pressure holding process, and a cooling process by performing a flow analysis using the flow analysis model;
a structural analysis unit that calculates shrinkage behavior of the resin based on the temperature information and the pressure information using the structural analysis model;
The apparatus for predicting warpage deformation of a resin injection molded product, wherein the structural analysis section sets the calculation start point of the shrinkage behavior calculation to the start point of the pressure holding process. A program for predicting warpage deformation of resin injection molded products using the finite element method through computer simulation,
to the computer,
step A of creating a flow analysis model and a structural analysis model by dividing the shape data of the mold cavity into a plurality of minute elements;
Step B of obtaining temperature information and pressure information of the resin in the injection process, pressure holding process, and cooling process by performing a flow analysis using the flow analysis model;
Using the structural analysis model, performing step C of calculating the shrinkage behavior of the resin based on the temperature information and the pressure information,
A program for predicting warp deformation of a resin injection molded product, characterized in that in step C, the calculation start point of the shrinkage behavior calculation is the start point of the pressure holding step. A computer-readable recording medium recording the program for predicting warp deformation of a resin injection molded product according to claim 13.